Compact Load Cell for Simultaneous Normal and Shear Force Measurement
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Solution Overview
Problem
Existing force sensing devices are limited in their ability to measure a wide range of forces, particularly in multiple degrees of freedom, and are not suitable for applications requiring precise measurement of normal and shear forces in a load plane offset from a sensor plane.
Innovation Solution
A compact load cell comprising at least three force sensing elements arranged in a sensor plane about a point, with each element having a pressure sensor encased in a force transmission medium, a load plate, and a load beam connected to the load plate, which transmits forces from the load plane to the sensor plane, allowing for simultaneous measurement of normal and shear forces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple barometric sensing devices are arranged in arrays to measure forces in multiple directions, then the measurement capability is improved, but the device complexity and size increase
Solution Approach 1:
The patent replaces complex mechanical force sensing arrays with pressure sensors that detect force through elastic deformation of an encapsulating material. This substitution simplifies the device architecture while maintaining the ability to measure forces in multiple directions through a single integrated sensor element rather than multiple discrete sensors.
Solution Approach 2:
The load cell design enables a single device to measure forces in multiple degrees of freedom (normal and shear forces in multiple directions) simultaneously. The force sensing element with its elastic encapsulation and offset load plane configuration provides universal force measurement capability without requiring separate sensor arrays for different force components.
2Adaptability or versatility
If force sensing devices use offset load planes to measure multiple force components, then the measurement versatility is improved, but the device size increases
Solution Approach 1:
The patent employs an elastic material encapsulation that acts as a flexible shell to transmit and distribute applied forces to the pressure sensing element. This flexible encapsulation enables the measurement of multiple force components (normal and shear forces) without requiring large mechanical structures, maintaining compact dimensions while achieving measurement versatility.
Solution Approach 2:
The invention utilizes an offset between the load plane and the sensor plane to enable measurement of multiple force components. By positioning the pressure sensing element at an offset from the load application plane, the device can resolve forces in multiple directions through the elastic deformation field, effectively using spatial dimensionality to achieve versatile measurement in a compact form.
3Measurement precision
If compact load cells use offset load planes, then measurement accuracy is improved, but the structural complexity increases
Solution Approach 1:
The patent achieves accurate force measurement by carefully controlling the offset distance parameter between the load plane and sensor plane. By optimizing this geometric parameter, the device can accurately resolve multiple force components without requiring complex mechanical structures. The measurement accuracy is achieved through parameter optimization rather than structural complexity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables accurate measurement of normal and shear forces in a load plane offset from the sensor plane, facilitating applications such as quadrotor UAV thrust and velocity determination, and providing a compact, lightweight solution for various industrial and robotic applications.
Implementation Method 1
Each force sensing element comprising a pressure sensor encased in a force transmission medium
Data Source
AI summary
A compact load cell that simultaneously measures normal and shear forces in a load plane offset from a sensor plane by a distance h. The compact load cell comprises at least three force sensing elements (preferably four) arranged in the sensor plane about a point and spaced a distance d from the point. All force sensing elements may be spaced by the same distance or the distance may be different for one or more force sensing elements. Each force sensing element comprises a pressure sensor encased in a force transmission medium. A load plate is in contact with the force transmission medium and a load beam is connected at one end to the load plate above the point of the sensor plane and extends to the load plane. Forces acting in the load plane are transmitted to the sensor plane by the load beam and load plate. The forces are resolved to determine the normal and shear forces acting at the load plane. The compact load cell may be applied to determine forces acting on, for example, an unmanned aerial vehicle.